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Photosynthesis in mesophyll protoplasts and bundle sheath cells of various types of C4 plants I. Carboxylases and CO2 fixation studies

1974; Elsevier BV; Volume: 72; Issue: 4 Linguagem: Inglês

10.1016/s0044-328x(74)80072-3

0044-328X

María Fernanda Gutiérrez, R. Kanai, Steven C. Huber, S. B. Ku, Gerald E. Edwards,

Plant Parasitism and Resistance

Mesophyll protoplasts and bundle sheath cells have been isolated from 3 groups of C4 plants by enzymatic digestion of leaves with cellulase and pectinase. In all species studied the phosphopyruvate carboxylase was localized almost exclusively in mesophyll cells, and ribulose-1, 5-diphosphate carboxylase in bundle sheath cells. Isolated bundle sheath cells from species having high NADP-malic enzyme activity showed varying degrees of light dependent fixation of CO2. Bundle sheath cells of sorghum and sugarcane showed little capacity for CO2 fixation while bundle sheath cells of Digitaria sanguinalis and Setaria lutescens showed substantial activity of light induced CO2 fixation. Similar or higher rates of CO2 fixation in the light were obtained with the isolated bundle sheath cells of C4 plants having low NADP-malic enzyme activity. The highest rate of CO2 fixation (103 μmoles/mg chl/hr) was obtained with bundle sheath cells of Panicum capillare. In all cases, there was a light induced fixation of CO2 by mesophyll protoplasts of C4 plants although the rates were low in comparison to the rates with isolated mesophyll protoplasts of C3 plants. The addition of phosphopyruvate to mesophyll protoplasts of C4 plants induced high rates of CO2 fixation. The results are discussed in relation to the proposed function of the C4-dicarboxylic acid pathway in C4 plants.